Reducing the mercaptan content of petroleum distillates with a hydroperoxide



Patented Apr. 22, 1952 REDUCING THE MERCAPTAN CONTENT OF PETROLEUM DISTILLATES WITH A HY- DROPEROXIDE Warren W. Johnstone, Riverside, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application February 21, 1950, Serial No. 145,601

10 Claims.

This invention relates to a process for sweeteni g sour petroleum distillates and particularly f rsweetening sour gasoline.

An object of this invention is to reduce the ercaptan content of a petroleum distillate conaining such organic sulfur compounds. V

A further object of this invention is to reduce the mercaptan content of a sourgasoline.

It is well known that the presence of organic sulfur compounds in gasoline lowers its lead susceptibility. That is, the introduction of lead tetraethyl causes a smaller improvement in the octane number of sour gasoline than would be obtained if the gasoline were free from-organic sulfur compounds. Accordingly, from th standpoint of lead susceptibility and sulfur reduction, it is usually considered best practice to extract mercaptans from gasoline rather than to convert them into the less-reactive disulfides by oxidation treatment. However, except in those distillates which contain mercaptans ofvery low molecular weights, it becomes costlyor uneconomical to extract all of; the mercaptans. Accordingly, it is'advantageous to operate an extraction process so as to remove from about 50 to about 99% of the mercaptans present and then to oxidize the remaining mercaptans to disulfides. According to this invention, organic peroxy compounds, particularly organic peroxides and organic hydroperoxides are utilized to oxidize these residual mercaptans or to convert them into compounds that do not give a positive reaction by the doctor test, that is, they do not give a precipitate of lead sulfide upon being treated with doctor solution which contains sodium plumbite, Na-aPbOz dissolved in caustic soda solution.

One embodiment of this invention relates to a process for reducing the mercaptan content of a sour petroleum distillate which comprises treating said distillate with an organic peroxy compound.

Another embodiment of this invention relates to a process for reducing the mercaptan content of a sour petroleum distillate which comprises treating said distillate with an organic hydroperoxide.

A further embodiment of this invention relates to a process which comprises extracting from about 50 to about 99% of the mercaptans from a sour petroleum distillate, oxidizing substantially all of the remaining mercaptans by treat ment with an organic hydroperoxide, and recovering a substantially mercaptan-free petroleum distillate.

2 A still further embodiment of this invention relates to a process for reducing the mercaptan content of a sour petroleum distillate which comprises treating said distillate with an organic peroxy compound and a catalyst comprising essentially a salt of an organic acid and of a metal selected from the group consisting of copper, cobalt, nickel, chromium, manganese, and iron.

This process may be used for reducing the mercaptan sulfur content of straight-run petroleum distillates including gasoline, kerosene, range oil, heater oil, and the like. The process is also applicable to cracked gasoline and naphtha. As the oxidation of the mercaptans results in the production of disulfides which are generally left in the gasoline or other petroleum distillate being treated, the sulfur content of this hydrocarbon material remains substantially unchanged after oxidation. As the lead susceptibility is improved by reducing the total sulfur content as well as by reducing the mercaptan content of the hydrocarbon distillate, it is desirable to extract the hydrocarbon material with caustic soda solution and preferably with caustic methanol solution to remove from about 50 to about 99% of the mercaptans. The remaining hydrocarbon material or rafiinate containing from about 1 to about 50% of the original mercaptans isthen treated by this process to oxidize mercaptans t g disulfides as illustrated by the following equation:v

zasn onsacoon 'iissn rngo oH3)30oH Alkyl t-butylhydro- Alkyl disulfidc mcrperoxide captan The organic peroxy compounds used as treat ing agents in this process contain the bivalent radical OO-. Examples of such compounds are peracetic acid, persuccinic acid, dimethyl ganic peroxy compounds constitute a preferred class of treating agents for use in this invention. Mixtures of peroxy compounds also may be em ployed.

The extraction of mercaptans from sour petroleum distillates is carried out by treating the hydrocarbon material with from about 5 to about 50% of its volume of caustic sodasolution containing from about 5 to about50 percent by' t-butyl alcohol weight of NaOH. Also an alcoholic solution of caustic soda is sometimes used to extract mercaptans from sour hydrocarbon oils. Thus a sour petroleum distillate is treated with from about 2 to about 5 percent by volume of a caustic-methanol solution formed by mixing 25 volumes of methanol with 75 volumes of aqueous sodium hydroxide solution of 48 Be. gravity.

The extraction with caustic soda solution is made at a temperature of from about 60 to about 110 F. and with caustic methanol solution at a temperature of from about 80 to about 110 F.

The resulting raifinate which contains from about 1 to about 50% of the mercaptans generally present in the sour distillate is then washed with water to remove residual caustic soda S0111.- tion and the water-washed raffinate is then mixed with an organic peroxy compound'in an amount sufiicient to convert th remaining mercaptans into disulfides and'the mixture is maintained at a temperature of from about 20 to about 350 F. and at'sufficient pressure tokeep thevhydrocarbon material in liquid phase. This heating with an organic peroxide or preferably an. organic hydroperoxide may be carried out under reflux, it may be effected also under pressure in an autoclave, or it may be carried out in a tubular reactor in which the hydrocarbonperoxide mixture is passed over heated quartz chips.

The hydrocarbon distillate which has been so treated with an'organic peroxide or hydroperoxide to reduce the'mercaptan content by convertinggor oxidizing mercaptans into disulfides, is then subjected to a further heat treatment or extraction, for example, with caustic to decompose or-to extract the excess of the organic peroxides remaining after the previous treating. This removal of residual peroxides is necessary in order to avoid loss of octane number over that of 'the hydrocarbon material which is free from organic sulfur compounds and peroxides.

This process for sweetening a sour petroleum distillate by treating with an organic peroxy compound and particularly with an organic hydroperoxide is also speeded up or accelerated by the presence-of a salt of an organic acid and of a metal and particularly the naphthenates and oleates oficopper, cobalt, nickel, chromium, manganese and iron. The metallic salt is used in an amount of from about 0.01 to 1.0 weight percent based on the organic peroxide used. The copper salts are preferred in this process. ever, when such metallic salts are used, it is also generally necessary to add a metal deactivator tothe hydrooarbonoil at the conclusion of the sweetening reaction in order to prevent the metal salt from catalyzing further oxidation reactions, said further oxidation reactions being obj ectionable. Metal deactivators which are, suitable for such use include the condensation products of salicylaldehyde with propylene diamine, orthoaminophenol and the like and. also tetra-acetic acid derivatives of ethylene diamine.

The nature of the present invention and types of results obtained thereby are also illustrated by thefollowing examples which should not be misconstrued as imposing undue limitations upon the generally broad scope of the invention.

EXAMPLE. I

Athermally cracked gasoline was treated with aqueouscaustie soda solution of 20-B. gravity in three stagesto reduce the mercaptan sulfurcontent' to 0.032% by weight. Then tertiary How- I butylhydroperoxide was added to the caustic treated gasoline in ten-fold excess of that calculated as necessary on the basis of one mole of hydroperoxide reacting with two moles of mercaptan, as indicated in the foregoingequation. This gasolin wasthen passed through a bed of quartz chips at a temperature of 260 F. and a liquid hourly space velocity of one and five. The resultant hydrocarbon product was sweet, that is, it was, free from mercaptan sulfur as shown both by the doctor test with sodium plumbite and by potentiometric titration with silver nitrate. The peroxide number of the treated hydrocarbon productuwas from 0.5 to 0.9 as compared with 36.5 for the charging stock. A blank run which was also made showed that the same gasoline, did not undergo sweetening reaction under. the same conditions but in the absence of tertiary butylhydroperoxide. Further work, however, indicated that the gasoline to which tertiary butylhydroperoxide was added would undergo sweetening when merely stored at room temperature (about 20 C.) for 24 hours. The large amount of peroxides remaining in the gasoline was 1 undesirable and accordingly further work was carried out to determine the minimum amount of tertiary butylhydroperoxide required to effect complete sweetening when gasoline was passedover quartz chips at a temperatureof approximately 265 F. at atmospheric pressure andusing a hydrocarbon charging rate correspond. ing to a liquid hourly space velocity of one. The

minimum amount of tertiary butylhydroperoxide was so found to be from 6.8 to 7.0 timesthe stoichiometric amount based upon one mole of hydroperoxidereactingwith two moles of mercaptans.

EXAMPLE II Chg; Stl-z. 'Product RSH Sul, Weight per cent 0. 045 nil Doctor .test Positive Negative Peroxide Number 1 48. 011

Color, Saybolt; +23 13 Vapor pressure, p. s. i. 6.7 5.0

Specific Gravity 60 0.7362 0. 7393 I. B. P 114 110.

I 0.3 times the calc. stoichiometric amount.

The above run was repeated, using a smallerv amount of tertiary butyl hydroperoxide and. a higher temperature (approx. 330 F.). sults shown below indicate a smaller color drop.

Chg. Stk; Product RSH Sul, weight per cent 0. 045 nil Doctor test Positive Negative Peroxide Number 1 33. 0 nil Color, Saybolt +23 +12 7: 6.3 0.7374 0. 7377 108 118 1 6.5 times the calculated stoichiornetric amount.

The re-.

EXAMPLE III 1 Another. cracked gasoline was first treated with caustic. methanol solution which reduced .the mercaptan content to 0.01%. It was found that heating wasunnecessary to cause sweetening of this gasoline with cumene hydroperoxide. At

room temperature a sample of caustic-methanol EXAIWPLE IV A sour heater oil boiling from 300 to about 600 F. was mixed with 6.5 times the calculated stoichiometric quantity of tertiary butylhydroperoxide needed for reacting with-the mercaptan content and the resultant mixture was heated at a temperature of 265 F. for 3.5 hours during which the mercaptan content was reduced from 0.073 weight percent in the charging stock to 0.028 weight per cent in the product. The same heater oil to which 6.5 times the calioulated' amount of tertiary butylhydroperoxide was added became sweet within thirteen days when stored at a temperature of 20 C. There was also a small decrease in the color of the heater oil during this treatment.

EXAMPLE V The straight run gasoline referred to in'Example II was distilled and the fraction boiling above 265 F. was sweetened when stored'at room temperature with 7.9 times the calculated quantity of tertiary butylhydroperoxide.

EXAMPLE VI This treating process was applied further to a stable sour cracked gasoline which had the inspection data shown in Table I.

Table I INSPECTION DATA ON some CRACKED GASOLINE Analyses:

Peroxide number 0.04 Mercaptan sulfur, weight percent 0.049 Hydrogen sulfide None Total sulfur, weight percent 0.17 Bromine number 24 Color, Saybolt +17 Phenols, weight percent (U. V.) 0.004

Thiophenols, weight percent (U. V.) 0.003 Total phenols, weight percent (U. V.) 0.007

A. S. T. M. gum, mg./100 ml 2 Oxygen bomb, Ind. Per., Min 95 Octane number, F-2 method clear 61.2

3 cc. TEL/gal 72.4 Reid vapor pressure, p. s. i. g 6.3 A. P. I. gravity 60 F. 59.5 I.B.P. F 99 5% 129 150 50 250 90 352 E, P, 412 Percent rec. 98.0 Percent Botts 1.0 Percent loss 1.0

As shown in the above table, this gasoline had a low A; S. T. M. gum content but had a rather high mercaptan content. This gasoline was par tially sweetened by a caustic-methanol treatment which reduced the mercaptan sulfur to 0.010%. This treated gasoline was then treated further withtwo times the stoichiometric amount of cumene hydroperoxide and stored in the dark at room temperature. The stoichiometric amount ofcumene hydroperoxide was-calculated on the basis 'of two moles of mercaptan reacting with one 'moleofcumene hydroperoxide to form one mole of disulfide, one mole of water, and one mole of phenyl-dimethyl carbinol. A sampleof the gasoline containing no added cumene hydroperoxide was stored at the same time as a blank. After twenty-two hours the gasoline containing the cumene hydroperoxide was found to be sweet, but still contained some peroxide as measured by the UOP method No. H-33-40. The residual peroxide was substantially removed by extrac- :tion with a strong alkaline reagent.

Properties of the caustic-methanol treated but still sour cracked gasoline and of this gasoline after sweetening treatment with cumene hydroperoxide are given inTable II. A hydrocarbon materialwhich contains mercaptans as indicated by the doctor testY'is said to be sour whereas a hydrocarbon product which does not give the doctor 'test. for mercaptans is referred to as a sweet product.

I Table II STABILITY DATA OF PEROXIDE SWEETENED RAW CRACKED GASOLINE ONE STAGE JET CAUSTIC- 'METHANOL TREATMENT 2 tlIltlBS stoich. g 1 am cumene Treatment None hydropemxide added Storage time and conditi0ns. J v Peroxide Number"; 0.03 0. 22 0.101 Swt. Positive Negative +11 +6 4 7 61. 6 60. 0 73. 7 73.6

39 29 3 14 5 29 Oxygen Bomb, Ind. Per., Mm;

Blank 110 +.0l0% UOP #4 225 715 +.006% UOP #5 n... 190 695 Reid Vapor Pressure, p. s. i. 6.0 5.8 A. P. I. Gravity 60 F 58. 9 58. 6 I. B. P. F 117 5% 142 147 10. 162 165 50 255 256 90" 353 352 95 378 377 E P 410 413 Per Cent Rec 98.0 98 5 Per Cent Bott 1. 0 l. 0 Per Cent Loss 1. 0 0.5

1 N-n-butyl-p-aininophenol.

4 N,N'-di-sec-butyl-p-phenylenediamine.

3 22 hours in dark at 70 F.

4 22 hours in dark at 70 F. alkali extraction oi residual peroxide.

The above results show that this particular sour gasoline can be sweetened by addition of twice the calculated amount of cumene hydroperoxide followed by room temperature storage. The sweetened and alkali extracted gasoline has good antiknock and stability characteristics.

I claim as my invention:

1. A process for reducing the mercaptan content of a sour petroleum distillate which comprises treating said distillate with an organic peroxy compound selected from the group consisting of tertiary butyl hydroperoxide and cumene 1 hydroperoxide.

7 tent of a sourpetroleum distillate which comprises treating said distillate with tertiary butyl hydroperoxide.

3. A process which comprises extracting from: about 50 to about 99% of the mercaptans fromav sour petroleum distillate, oxidizing substantiallyall of the remaining mercaptans by treatment with an organic hydroperoxide selected fromthe group consisting of tertiary butyl hydroperoxideand cumene hydroperoxide, and recovering a substantially mercaptan-free petroleum distillate.

4. A process for reducing the mercaptan content of a sour petroleum distillate which com-f prises treating said distillate with an organic, peroxy compound selected from the group con,- sisting of tertiary butyl hydroperoxide and] cu.-

mene hydroperoxide at a temperature of fromv about 20 to about 350 F.

5. A process which comprises extracting from about 50 to about 99% of the mercaptans'froma sour petroleum distillate, oxidizing substantially allof the remaining mercaptans by treatment with tertiary butyl'hydroperoxideat a temperature of from about 20 to about 350 F. andrecovering a substantially mercaptan-freepetroleum distillate.

6. A process for reducing the-'mercaptan content of a sour petroleum distillate which comeprises treating said distillate with an organic peroxy compound selected from the group consisting of tertiary butyl hydroperoxide and cumene hydroperoxide and a catalyst comprising essentially a salt of an organic acid and of a metal selected from the group consisting of copper, cobalt, nickel, chromium, manganese, and iron.

7. A process for reducing the mercaptan'content of a sour petroleum distillate which comprises treating said distillate at a temperature of from about 20 to about 350 F. with an organicperoxy compound selected from the group consisting of tertiary butyl hydroperoxide and cumene hydroperoxide and acatalyst comprising essentially a salt. of an organic acid and of a metal selected from the group consisting of copper, cobalt, nickel, chromium, manganese, and iron.

8. A process for reducing the mercaptan content; of a sour petroleum distillate which com:-

prises treating said distillate with tertiary butyl,

hydroperoxide ata temperature of from about20 to'about 350 F.

9. A process for reducing the mercaptan content of a sour petroleum distillate which come :prises treating said, distillate with cumene hy- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,840,269 Borgestrom Jan. 5, 1932 2,036,396 Chebotar. Apr. '7, 1936 2,208,509 Blairetal July 16, 1940 2,427,212 Henderson Sept. 9, 1947 FOREIGN PATENTS Number Country Date 615,561 Germany Dec. 5, 1936 

1. A PROCESS FOR REDUCING THE MERCAPTAN CONTENT OIF A SOUR PETROLEUM DISTILLATE WHICH COMPRISES TREATING SAID DISTILLATE WITH AN ORGANIC PEROXY COMPOUND SELECTED FROM THE GROUP CONSISTING OF TERTIARY BUTYL HYDROPEROXIDE AND CUMENE HYDROPEROXIDE. 